1. Field of the Invention
The present invention relates to a high-voltage transformer coil with acoustic wave guiding function, and more particularly to a high-voltage coil with a wave guide which comprises protrusions and inner caves arranged alternately, so that the acoustic waves generated due to discharge can be well transmitted to a measuring device without damage thereto; and the present invention is preferably suitable for a cast resin transformer.
2. Related Prior Arts
For manufacturers, properties of electrical power, such as stability, are important to prolong life of equipment and maintain quality of products. Unstable power or unpredictable shutting off do not facilitate yield and even result in lots of waste product. In high-technological processes, it's much desired for good and stable power supplying due to high-priced product and high cost thereof.
Currently, electrical power generated in the power plant is first transmitted to substations via high-voltage power cables, and then delivered to different areas via distributors, and finally to respective users after using transformer to decrease voltage.
The traditional oil-immersed transformer is primarily assembled by an iron core and a coil which contains insulated oil therein to increase insulation and heat-dissipation of the transformer. To prolong life of the transformer, the insulated oil should be changed after using for a certain period, and thus cost for maintenance is increased. Once the transformer is too hot and sparks at a temperature over the flame point of the insulated oil, the insulated oil will burns and the transformer could explode. Such phenomenon is dangerous and results in disrupture of the plants. Therefore, the oil-immersed transformer is gradually replaced with the cast resin transformer for safety.
As shown in FIGS. 3 and 4, a high-voltage-coil set (9) of the cast resin transformer comprises a iron core (91) formed by a plurality of stacked silicon steel sheets and wound with wires to form three high-voltage coils (92). The three high-voltage coils (92) are embedded with insulated resin (not shown in figures) to form the high-voltage-coil set (9) of the cast resin transformer. Each of the high-voltage coils (92) is primarily constructed by wound wires (921) which are embedded with insulated material (922) to form an annular coil. The high-voltage coil (92) further comprises a high-voltage connector (923) which is composed of terminals (924) and high-voltage contacts (925). Heat-dissipation is achieved by air convection in the high-voltage coil (92). Compared with the traditional oil-immersed transformer, the cast resin transformer needs no oil and is safer without flaming. In addition, the cast resin transformer exhibits merits of moisture-proof, less noise and flame-retardant, and thus is suitable for application in hospitals, high-technological plants, express and air service.
Maintenance and fault-detection for power equipment are also very important. For the cast resin transformer, malfunctions generally caused by poor insulation of the high-voltage coil and thus partial discharge occurs. If no detection is provided in time, resin of the high-voltage coil in the cast resin transformer will be rifted and operations of the plant could be disrupted.
FIG. 5 shows the partial discharge similar to pulses which generate mechanical pressure waves as acoustic emission. Such phenomenon could be caused by collision between molecules of material and adjacent structures, and form a sound source (93) to emit acoustic waves. These acoustic waves will emit inside the equipment and thus can be detected with an acoustic emission (AE) method. By attaching an AE sensor (94) to the surface of the transformer, the piezoelectric material inside the AE sensor (94) will transform the AE signals of mechanical pressure waves into electrical signals which are then amplified with a preamplifier (96). A digital oscilloscope (97) is provided to analyze the acoustic emission signals and therefore statuses of the equipment can be predicted.
For the AE method applied to the high-voltage coil, some issues should be noticed as follows:
1. Decaying of the Acoustic Waves
During producing the high-voltage coil, interspace of the molds is filled with glass fiber for associating with resin to increase mechanical strength thereof. However, glass fiber can absorb the acoustic waves, which will results in decaying of the acoustic waves during transmitting in the high-voltage coil. Therefore, it's important to solve the above problem when utilizing the AE method to detect partial discharge.
2. Damage to the Measuring Device or the Transformer
When attaching the probe of the measuring device to surfaces of the high-voltage coils, the distance between the coil and the probe is about only 3mm. Therefore, high potential is formed between them for high-voltage input, which may cause the coil to generate corona discharge to the probe and misguide the detection; and even more seriously cause damage of the transformer and measuring device.
The present invention therefore develops a high-voltage coil for transmitting acoustic waves to a measuring device so as to improve demerits aforementioned.